It’s not like you can hold the other end to keep it steady. A foam cutter built like a coping saw but held parallel to the wire would offer much better control. [Techgenie]’s handheld hot wire ...

so he built a low-rider foam cutter. With the mattresses laying on the ground, the idea was to have the cutter simply roll across them. The cutter uses a 45″ (115 cm) long 14 AWG nichrome wire ...